Electric contact grease

ABSTRACT

AN ELECTRIC CONTACT GREASE CONSISTING ESSENTIALLY OF:   (A) A MAJOR AMOUNT OF PARAFFINIC MINERAL OIL, (B) 2 TO 15 PERCENT BY WEIGHT OF CHLORINATED DIPHENYLS AND TRIPHENYLS, (C) 7 TO 12 PERCENT BY WEIGHT OF COLLOIDAL SILICA, AND (D) 0.1 TO 3.0 PERCENT BY WEIGHT OF AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF (I) AMINO COMPOUNDS HAVING THE FOLLOWING FORMULA:   1-(R1-NH-),2-(R2-NH-)BENZENE   WHEREIN R1 IS ALKYL CONTAINING 3 TO 10 CARBON ATOMS, AND R2 IS A MEMBER SELECTED FROM THE GROUP CONSISING OF ALKYL CONTAINING 3 TO 10 CARBON ATOMS, CYCLOALKYL AND ARYL, AND (II) AMINO COMPOUNDS HAVING THE FOLLOWING FORMULA:   (4-(R1-N(-R2)-)PHENYL)2-CH2   WHEREIN R1 AND R2 ARE ALKYL CONTAINING 1 TO 10 CARBON ATOMS, RESPECTIVELY.

Consumed energy due to fluctuqtion of contact resistance (ergs) Nov. 27, 1973 AKIRA INAMI ET AL ELECTRIC CONTACT GREASE Filed June 19fi972 Number of tim s of sliding action United States Patent Int. Cl. mom's/2o. /26 us. Cl. 252-11 ABSTRACT OF THE DISCLOSURE An electric contact grease consisting essentially of:

(a) a major amount of parafiinic mineral oil,

(b) 2 to percent by weight of chlorinated diphenyls and triphenyls,

(c) 7 to 12 percent by Weight of colloidal silica, and

(d) 0.1 to 3.0 percent by weight of at least one member selected from the group consisting of (i) amino compounds having the following formula:

wherein R, is alkyl containing 3 to 10 carbon atoms,

and R, is a member selected from the group consisting of alkyl containing 3 to 10 carbon atoms, cycloalkyl and ml, and (ii) amino compounds having the following formula:

Rs t Q- Q- Ih Rs wherein R, and R, are alkyl containing 1 to 10 carbon atoms, respectively.

new or THE INVENTION The present invention relates to an electric contact grease which has particular application in sliding contacts of electrical machines and apparatuses.

DESCRIPTION OF THE PRIOR ART Conventional electric contacts in, for example, television and radio are subjected to contact failure and are responsible for troubles such as sound noise, picture failure and the like.

These troubles are prevented to some extent by using electric contact greases. However, conventional grease for an electric contact has not been completely satisfactory due to the complicated nature of the phenomenon of the electric contact. 1

Contact failure is usually caused by oxidation, sulphurization and wear of contact metal surfaces and sludge formed by oxidation and polymerization of grease itself used for the contact. Therefore, the role of contact grease is to prevent oxidation, sulphurization and wear of con- 4 Claims Iii tact metals so as to stabilize the electric contact resistance, to prevent noise and to lengthen the life of the electric contact.

' BRIEF SUMMARY OF THEINVENTION An object of the present invention is to provide a contact grease capable of preventing wear of the electric sliding contact.

A contact grease according to the present invention com- 3,775,317 Patented Nov. 27, 1973 "ice Another object of the present invention is to provide a contact grease which stabilizes contact resistance and thereby prevents noise in the electric contact.

A further object of theprcsent invention is to provide a contact grease which prevents damage to electric contacts, due to variable circumstances. These and other objects of the present invention will be apparent upon consideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the relationship between the number of times of sliding action and the stability of electrical contact resistance.

DETAILED DESCRIPTION A contact grease according to the present invention consists essentially of a major amount of a paraffinic mineral oil, 2 to 15 percent by weight of chlorinated aromatic hydrocarbon, 7 to 12 percent by weight of colloidal silica and 0.1 to 3.0 percent by weight of at least one member selected from the group consisting of (i) amino compounds having the following formula:

wherein R, is alkyl containing 3 to 10 carbon atoms, and R, is a member selected from the group consisting of alkyl containing 3 to 10 carbon atoms, cycloalkyl and aryl, and (ii) amino compounds having the following formula:

t Rs wherein R, and R, are alkyl containing 1 to 10 carbon atoms, respectively.

Anti-rust agent or anti-sulphurizing agents are preferably added to the composition of the grease.

The novel contact grease according to the present incontact metal because of its good chemical stability and a mechanical characteristics though its electric resistivity is comparably higher.

Paraflinic mineral oil defined herein includes pure para flinic mineral oil having a small amount, for example, up to '20 percent by weight of aromatic and/or naphthenic mineral oil incorporated therein. It is preferable that the paralfinic mineral oil has a viscosity of 50 to 140 centistoltes (at 37.8 C.) and an aniline point higher than in .the ASTM 06ll-55T (American Society for Testing Materials).

A paraftinic mineral oil having a viscosity iower than I 50 est. results in a contact grease which has poor antiwearing property, and higher than est. results in contact grease which has poor stability of contact resistance. Paraflinic mineral oil which has aniline point lower than about 95 results in contact grease which has a tendency towards noise occurrence at comparably high temperature.

prises chlorinated aromatic hydrocarbon, i.e., at least one member selected from the group consisting of tetrachlorodiphenyl, pentachlorodiphenyl, hexachlorodiphenyl and polychlorotriphenyl. When the chlorinated aromatic hydrocarbon is present in an amount higher than about percent by weight, the electric contact resistance is diiiicult to stabilize. At an amountof the chlorinated aromatic hydrocarbon lower than 2 percent by weight, the antiwearing property of the grease becomes smaller.

The contact grease according to the present invention, also comprises colloidal silica having a BET-surface area (surface area measured by BET method) of from 180 to 330 mF/g.

when the amount of colloidal silica is lower than about 7 percent by weight, the life of the contact becomes shorter. When that amount is higher than 12 percent by weight, the wear of the contact metal becomes larger.

in the present invention, the amino compound as antioxidant not only serves to prevent mineral oil from oxidation and polymerization, but at the same time decreases the wear of the contact metal and stabilizes the contact resistance.

On the other hand, in the case of other antioxidants, for example, 4,4'-methylcne-bis-(2,6-di-tert-butyl phenol) or, 2,6-di-tcrt-butyl para-cresol, the contact resistance is low in the first stage of sliding action, but the wear advances rapidly with the progress of sliding action. Consequently. the contact resistance becomes larger and noise is genernted.

The contact grease using silicone oil as base oil is inferior to the grease according to the present invention in the anti-wearing property.

According to the present invention, a mixture of the paraffinie mineral oil, the chlorinated diphenyl, and the amino compound with or without rust inhibitor and antisulphurizing agent is heated at 120 to 150 C. to make a homogeneous liquid, and then the colloidal silica is added thereto under stirring to make a homogeneous paste. The cooled mixture is milled by a usual method, e.g. employing three roll mills, and is subjected to a reduced pressure so as to remove air and foam. The resulting greases are smooth and buttery in texture and have excellently mechanical and thermal stability. The invention is described in the following examples, which are for the purpose of i1- !ustration and are not considered to be limitativc with respect to scope or conditions. In the example, g." represents grams.

Example 1 A mixture of 81.5 g. of parafiinic mineral oil having viscosity of 65 cst.at 37.8 C. and aniline point of 98.2 C., 70 g. of tctrachloro diphenyl and 2.0 g. of N,N,N',N- tetramethyi-4,4'-diamino-dipheuyi methane (tetra base) is heated at about 130 C.

After being homogenized, 9.5 g. of Aerosil-300 (trade name of colloidal silica having'BET surface area of about 300 m./g., which is manufactured by Japan Aerosil Company Ltd.) is added to the mixture under stirring.

After being homogenized. the mixture is cooled to room temperature and milled with three roll mill. Then the foam remaining in the grease is removed under reduced pressure. The resulting grease is stable and has a pour point of higher than 230' C. The grease is applied to an electric contact. t

The grease action is shown in Example No. 1 of Table 1 and FIG. 1.

Example 2 A mixture of 74.5 g.- of paraflinic mineral oil having viscosity of 110.2 cat. at 37.8 C. and aniline point of 113.0 C., 12.5 3.01 hexachlorodiphenyl and 1.8g..o1 N,N'-di-sec-butyi-paraphenylene diamine is heated at about 150' C. 7

After being homogenized, 11.2 g. of Aerosil-300 is added to the mixture under stirring.

4 The resulting mixture is treated in a way similar to that of Example 1: The test is carried out similarly to Example 1 and the result is shown in Table 1 and FIG. 1.

Example 3 of Acrosil-200 (having BET surface area of about 200 mF/g.) is added thereto and the mixture is treated in a way similar to Example l.

The test is carried out similarly to Example 1 and the result is shown in Table 1 and FIG. 1.

Example 4 The mixture of 85.6 g. of parafiinic mineral oil having viscosity of 104.3 cat. at 37.8 C. and aniline point of 105.2 C., 2.0 g. of tetrachlorodiphenyl and 1.9 g. of

N,N'-di-sec-hexyl-paraphenylene diamine is heated at 130 C.

After being homogenized, 10.5 g. of Aerosil-300 is added thereto and the mixture is treated in a way similar 7 v to Example 1.

The resting result is shown in Table 1 and FIG. 1.

) Example 5 The mixture of 78.2 g. of paraffinic mineral oil having viscosity of 110.1 cst. at 37.8" C. and aniline point of 112.1 C., 12.0 g. of heptachlorodiphenyl and 0.2 g. of N, N"di-sec-hexyl-para-phcnylene diamine is heated at 145' C. 7

After being homogenized, 9.7 g. of Aerosil-200 is added thereto and the mixture is treated in a way similar to Example 1. The testing result is shown in Table 1 and FIG. 1.

Example 6 The mixture of 76.7 g. of paraflinic mineral oil having viscosity of 134.2 cst. at 37.8 C., 10.0 g. of hcxachlorodiphenyl, and 3.0 g. of N,N'-dimethyl-N,N'-dioctyl-4,4' diamino diph'enyl methane is heated at C. After being homogenized, 10.3 g. of Aerosil-300 is added hereto and the mixture is treated in a way similar to Example 1.

The testing result is shown in Table 1 and FIG. 1.

Example The mixture of 85.2 g. of paraflinic mineral oil having viscosity of 55.2 cst. and aniline point of 96.3 C, 4.5 g. of tetrachiorodiphenyl and 0.5 g. of N-isopropyl-N'- phcnyl-para-phenylene-diamine is heated at C.

"After being thereto and, the mixture is treated in a way similar to Example 1.

The testing result is shown in Table 1 and FIG. 1.

Example 8 Example 1.

The testing result is shown in Table 1 andFIG. 1.

Example 9 The mixture of 808g. of parafiinic mineral oil having viscosity of 82.5 cst. at37.8 C. and aniline point of homogenized, 9.8 g. of Aerosil-300 is added l02.5 C., 8.5 g. of hexachlorodiphenyl and 2.0 g. of tetra base is heated at 140' C.

After being homogenized, 8.7 g. of Aerosil-200 is added thereto and the mixture is treated in a way similar to Example 1. a

The testing result is shown in Table l and FIG. 1.

Example The mixture of 83.1 g. of paraflinic mineral oil having viscosity of 98.5 cst. and aniline point of 112.0 C., 1

Example 11 The mixture of 80.8 g. of paraflinic mineral oil having VlSCOSliy of 77.5 est. and aniline point of 108.2 C., 7.3 g. of hcxachlorodiphenyl and 2.5 g. of N,N'di-sec-butylpara-phenylene diamine is heated at 140' C.

After being homogenized, 9.4 g. of Aerosil-249l is added thereto and the 'mixture is treated in a way similar to Example 1.

The testing result is shown in Table l and FIG. 1.

Table 1 shows the test results of antiwearing property of the greases of from Example 1 to 11 and commercially available conventional greases for comparison.

The test was carried out as follows.

The greases were applied to the sliding contact which comprises a combination of a movable contact rivet and fixed contact plate. The material used for the fixed contact plate is nicltei.

The radius of curvature of the top of the movable contact rivet is 2 mm. The rivet is madeof at least one member selected from the group consisting of platinum, gold, silver, copper and their alloys. The wear of the contact rivet was measured as decreased thickness of the top of the rivet after 50 thousand times of sliding action with sliding speed of 8 cm./sec. and sliding distance of 4 cm.

As the value of the electrical contact resistance fluctuates with sliding action, the peak value of contact resistance has little meaning.

Therefore, the energy E that was consumed at the contact in a given time was counted.

Energy E is expressed as follows.

t E-J; tRcc-it (1) i: contact current measured t: time measured Rc: Electric contact resistance In the present case, the condition is as follows. i=50 ma. i=1 sec.

The reference numbers 1 to 19 in FIG. 1 correspond to the test number in Table 1, respectively.

Generally speaking, the difference between the contact resistance before and after sliding action should not be large in order to be used effectively for electric contact.

It is clear from FIG. 1 that the grease according to the present invention has little difference between the contact resistance at the beginning and after 50 thousand times of sliding action.

Consequently, the grease according to the present invention provides an electric contact having a stable contact resistivity, with prevention of noise generation completely and lengthening the life of the electric contact.

TABLE 1 Wear of Comcontact presslve rivet load of (thick contact Material of uses) No. Sample of grease (g.) contact rivet (mm.)

1 Example 1 0. 036 2 Fxnmple 2 0. 02'. Example 8 0. 0'15 Example 4 0.032 Example 5 0. 027 Example 0 0015 Example 7. 0. (H3 Example 8. 0.010 Example 0. 0. 024 lo 10 0. 023 in ii 0.021! Li-sonp grease 0. 0l8 Silicone grease 0.070 Grease containing 0.048

M iii 1 instead of tetra base I in r 20 Ag 0. cos d 400 Ag 0. 058 Ag-Cu (00-10). 0.018 100 An-A -Pt 0. 010

(00-' H3). 100 Nickel sliver. 0. 012

l MBP-4, 4'-methyleno his (2.0-dl-tert. butyl phenol). Tetra base-4,4'-tetramethyldiamlnodlphenylmethana.

We claim:

1. A contact grease consisting essentially of (a) a major amount of parafiinic mineral oil,

(b) 2 to 15 percent by weight of at least one chlorinated aromatic hydrocarbon selected from the group consisting of chlorinated diphenyl and chlorinated triphenyl,

(c) 7 to 12 percent by weight of colloidal silica, and

(d) 0.1 to 3.0 percent by weight of at least one member selected from the group consisting of (i) amino compounds having the following formula:

wherein R, is alkyl containing 3 to 10 carbon atoms,

and R, is a member selected from the group consisting of alkyl containing 3 to 10 carbon atoms, cycloalkyl and phenyl and (ii) amino compounds having the following formula:

on l

Rs 7 Rs wherein R and R, are ailtyl containing 1 to 10 carbon atoms, respectively.

2. A contact grease of claim 1, wherein said parafiinic mineral oil has viscosity of 50 to centistokes at a temperature of 37.8 C. and aniline point of higher than 950 3. A contact grease of claim 1, wherein said chlorinated aromatic hydrocarbon is a member selected from the group consisting of tetrachlorodlphenyl, pentachlorodiphenyl, hexachlorodiphenyl and polychlorotriphenyl.

4. A contact grease of claim 1, wherein said colloidal silica has BET surface area of from to 330 m3/g.

References Cited UNITED STATES PATENTS 2,887,369 5/1959 Thompson 252-50 2,898,295 8/1959 MacKenzie 252-28 3,288,711 11/1966 Knowles et al. 252-28 3,349,034 10/1967 Butcock et al. 252-28 DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner U.S. Cl. X.R. 

